<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <script src="http://libs.baidu.com/jquery/1.10.2/jquery.min.js"></script>
    <script type="text/javascript">
        var countdown=60;
        function sendemail(){
            var obj = $("#btn");
            settime(obj);

        }
        function settime(obj) { //发送验证码倒计时
            if (countdown == 0) {
                obj.attr('disabled',false);
                //obj.removeattr("disabled");
                obj.val("免费获取验证码");
                countdown = 60;
                return;
            } else {
                obj.attr('disabled',true);
                obj.val("重新发送(" + countdown + ")");
                countdown--;
            }
            setTimeout(function() {
                    settime(obj) }
                ,1000)
        }
    </script>
<body>
<input type="button" id="btn" value="免费获取验证码" onclick="sendemail()" />

</body>
</html>